1. Field of the Invention
The present invention relates to a liquid crystal display keyboard having a transparent keyboard on a liquid crystal display.
2. Description of the Prior Art
A structure of a prior art liquid crystal display keyboard is shown in FIG. 1.
In FIG. 1, numeral 1 denotes a liquid crystal display having a polarizing plate 2 bonded thereon and a transparent conductive film 3 bonded thereon.
A plurality of stripe-shaped transparent electrodes 4 are formed on the transparent conductive film 3.
The transparent electrodes 4 are formed by depositing indium oxide on an entire surface of the transparent conductive film 3 by sputtering or vacuum deposition techniques and etching it to a predetermined pattern to form the transparent stripe electrodes.
A frame-shaped spacer 5 is bonded to an upper surface of the liquid crystal 1 to surround the polarizing plate 2 and the transparent conductive film 3, and another transparent conductive film 6 is bonded to top edges of the spacer 5. Transparent stripe electrodes 7 are formed on the lower surface of the transparent conductive film 6 to be transverse to the underlying transparent electrodes 4.
The upper and lower transparent electrodes 4 and 7 are spaced by the spacer 5 and crosspoints of those formed key input areas.
In order to input a key data, the upper transparent conductive film 6 is depressed by a special pen P as shown in FIG. 2 to bring the upper and lower transparent electrodes 4 and 7 into contact.
However, when the upper transparent conductive film 6 is depressed by the pen P, the transparent conductive film 6 and the transparent electrodes 7 are bent with a relatively large radius of curvature so that a relatively large force is concentrated to the lower transparent electrode 4.
As a result, the lower transparent electrodes 4 are bent. The transparent electrodes 4 have poor adhesivity to the transparent conductive film 3 and as they are bent a number of times, they are broken and the key entry is disabled.
When a character is drawn by the pen P to recognize a pattern, the pen is slid. As a result, a small wave is created in the transparent conductive film 6 which pen P contacts. The transparent electrodes 4 are correspondingly depressed and their durability is lowered to an extent that they cannot operate correctly.